It is well understood and recognized that tracked vehicles have better traction than vehicles relying merely on drive wheels in muddy, sandy or otherwise difficult terrain wherein wheeled vehicles become bogged down. Consequently, there have been attempts in the prior art to modify wheeled vehicles to all terrain vehicles. One such example, of which applicant is aware, is Canadian Patent No. 962,303 which issued Feb. 4, 1975 to Russell for a modification means for changing wheeled vehicles to all terrain vehicles. Russell teaches providing a plurality of cylinders with means for affixing one each of the cylinders to the wheels of the vehicle. A plurality of flat endless belts, each having a plurality of tires affixed to the outer surface thereof in flat adjacent relationship with the endless belts affixed in overlying relationship on the cylinders so as to rotate with the wheels of the vehicle.
In the art of tracked vehicles generally, applicant is aware of the following Canadian Patents: Patent No. 580,645, which issued Aug. 4, 1959, to Benson for a Pneumatic Track; Patent No. 514,985 which issued Oct. 26, 1943, to Walker for a Pneumatically Mounted Tractor; Patent No. 580,651, which issued Aug. 4, 1959, to Eger for a Pneumatic Track; Patent No. 713,969, which issued Jul. 20, 1965, to Bonmartini for a Vehicle Track with Protected Joints; Patent No. 849,411, which issued Aug. 18, 1970, to Hartlerode for a Track Construction for a Track Laying Vehicle; Patent No. 950,947, which issued Jul. 9, 1974, to Ferguson for a Support Unit for Crawler Vehicle Track; Patent No. 1,260,994, which issued Sep. 26, 1989, to Burmeister for a Mattress Construction for Pneumatic Mattress Track System; Patent No. 1,293,757, which issued Dec. 31, 1991, to Kadela for an All Terrain Off Road Vehicle; Patent No. 797,114, which issued Oct. 22, 1968, to Ferguson for a Track Apparatus for Crawler Type Vehicles; and Patent No. 1,233,493, which issued Mar. 1, 1988, to Bertelsen for a Segmented Air Track Apparatus.
In other track related art, applicant is aware of U.S. Pat. No. 3,948,707, which issued Apr. 6, 1976, to Grawley et al for a Flexible Sealed Track Belt; U.S. Pat. No. 3,244,458, which issued to Frost for an Inflatable Endless Belt and Support Therefor; U.S. Pat. No. 3,170,533, which issued Feb. 23, 1965, to Fewel for a Vehicle with Pneumatic Support; U.S. Pat. No. 5,284,387, which issued Feb. 8, 1994, to Loegering for a Removable Flexible Track Belt and Track Section Therefore; U.S. Pat. No. 3,602,364, which issued Aug. 31, 1971, to Magleo for a Segmented Belt; U.S. Pat. No. 4,810,043, which issued to McIntosh for a Tire-Located Track; U.S. Pat. No. 4,089,565, which issued to Loegering for a Removable Track Structure for Wheeled Vehicles; U.S. Pat. No. 5,388,624, which issued Feb. 14, 1995, to Nordstrom et al for a Vehicle Driven Wheel With Tire and Track Driven Thereby.
As taught by Loegering in U.S. Pat. No. 5,284,387, the use of an endless track as a traction enhancer for wheeled vehicles is well known. Typically, such belts comprise a plurality of individual track sections that are linked together for pivotal movement with respect to adjacent track sections. These track belts have traditionally been used to obtain better overall traction for the vehicle generally, and in wet and slippery conditions particularly. Single pivot linkage mechanisms are often used where the tires of the vehicle are extremely rounded, where three or more wheels will have a flexible belt mounted to them, or where there is a long wheelbase between adjacent wheels. In those circumstances, a single pivot linkage mechanism is usually more desirable because the single pivots rock and flex less than the known double pivot linkages; that is, they are more rigid than the double or dual pivot linkage, and therefore prevent substantial side tilting of the track sections and, therefore, the vehicle tires are less likely to walk out of the track belt.
As further taught by Loegering, generally, each of the track sections include a base pad structure having an elongate shape that engages the ground during operation of the vehicle. The base pad forms a cross bar that extends between a pair of opposed side walls, which in turn extend upwardly from the base pad on opposite longitudinally spaced ends thereof. Adjacent track sections are linked together by a linkage mechanism. During operation of a vehicle utilizing such flexible belts, the vehicle tires are normally guided within the track sections by the side walls of the track section. The prior art track sections usually guide the tires by engaging the soft sidewall of the tire, resulting in side wall wear on the tire. In addition, during normal operation, the vehicle will often experience forces directed sideways to the track belt, or along the longitudinal direction of extent of the individual track sections. When experiencing these side loading forces, the tires will tend to crawl upwardly along the sidewall of the track section. This side loading of the tires into the sidewall of the track section creates wear on the tire, in particular on the tire sidewall, which is usually thinner and softer than the tire tread and thus more susceptible to wear.
On uneven terrain, such as where rocks are encountered by one side of a track section, the track belt can experience significant rocking and flexing of the individual track sections relative to adjacent track sections, or of an end of a single track section relative to the other end thereof. This rocking and flexing of the track sections also contributes to tire wear, as well as significant wear on the linkage mechanism connecting adjacent track sections. That is, when an object is encountered by one side of the track section, the track section will tend to tilt. Since it is rigidly, and often integrally attached at one end of the link, however, tilting of the track section is inhibited and the tilting load is transferred to the linkage pin, which can cause accelerated wear on the linkages. The pin in effect acts as a saw, increasing the wear. This is particularly true for single pin linkages. Known double pivot linkages are relatively more flexible, but facilitate the tire wheels walking out of the track belt.